package com.ctgu.tengyun.util;

/* 
 * Password Hashing With PBKDF2 (http://crackstation.net/hashing-security.htm).
 * Copyright (c) 2013, Taylor Hornby
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, 
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation 
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 */

import com.ctgu.tengyun.exception.TengyunRuntimeException;

import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.math.BigInteger;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

/*
 * PBKDF2 salted password hashing.
 * Author: havoc AT defuse.ca
 * www: http://crackstation.net/hashing-security.htm
 */
public class PasswordUtil
{
    public static final String PBKDF2_ALGORITHM = "PBKDF2WithHmacSHA1";

    // The following constants may be changed without breaking existing hashes.
    public static final int SALT_BYTE_SIZE = 32;
    public static final int HASH_BYTE_SIZE = 32;
    public static final int PBKDF2_ITERATIONS = 1000;

    private static Character[] aToZ = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
    	'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
    	'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I',
    	'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
    	'X', 'Y', 'Z' };  
    
    static Character[] numbers = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
    
    static Character[] specials = {'~', '`', '@', '#', '$', '%', '^', '&', '*', '-', 
    		'_', '=', '+', '|', '\\', '?', '/', '(', ')', '<', '>', '[', 
    		']', '{', '}', '\'', ',', '.', ',', ';', '\"', '!'};
    
    private static Set<Character> passwordChars = new HashSet<Character>(128);
    static{
    	passwordChars.addAll(new HashSet<Character>(Arrays.asList(aToZ)));
    	passwordChars.addAll(new HashSet<Character>(Arrays.asList(numbers)));
    	passwordChars.addAll(new HashSet<Character>(Arrays.asList(specials)));
    }
   
    
	public static boolean checkPasswordStrength(String password) {
		// TODO more constrain...
		if (null == password || password.length() < 6 || password.length() > 128){
			return false;
		}
		
		for (int i=0; i < password.length(); i++){
			if (!passwordChars.contains(password.charAt(i))){
				return false;
			}
		}
		
		return true;
	}
	
    /**
     * Returns a salted PBKDF2 hash of the password.
     *
     * @param   password    the password to hash
     * @return              a salted PBKDF2 hash of the password
     */
    public static String createHash(String password, String salt)
    {
        try {
			return createHash(password.toCharArray(), fromHex(salt));
		} catch (NoSuchAlgorithmException e) {
			throw new TengyunRuntimeException("create hash error.", e);
		} catch (InvalidKeySpecException e) {
			throw new TengyunRuntimeException("create hash error.", e);
		}
    }

    
    public static String getSecureRandom(){
    	 // Generate a random salt
        SecureRandom random = new SecureRandom();
        byte[] salt = new byte[SALT_BYTE_SIZE];
        random.nextBytes(salt);
        
        return toHex(salt);
    }
    
    /**
     * Returns a salted PBKDF2 hash of the password.
     *
     * @param   password    the password to hash
     * @return              a salted PBKDF2 hash of the password
     */
    private static String createHash(char[] password, byte[] salt)
        throws NoSuchAlgorithmException, InvalidKeySpecException
    {
        // Hash the password
        byte[] hash = pbkdf2(password, salt, PBKDF2_ITERATIONS, HASH_BYTE_SIZE);
        // format hash
        return toHex(hash);
    }

    /**
     * @param inputPassword the password to check
     * @param currentSalt
     * @param correctHash the hash of the valid password
     * @return 
     * 			true if the password is correct, false if not
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    public static boolean validatePassword(String inputPassword, String currentSalt, String correctHash)
        throws NoSuchAlgorithmException, InvalidKeySpecException
    {
        byte[] hash = fromHex(correctHash);
        char[] pwd = inputPassword.toCharArray();
        byte[] salt = fromHex(currentSalt);
        // Compute the hash of the provided password, using the same salt, 
        // iteration count, and hash length
        byte[] testHash = pbkdf2(pwd, salt, PBKDF2_ITERATIONS, hash.length);
        // Compare the hashes in constant time. The password is correct if
        // both hashes match.
        return slowEquals(hash, testHash);
    }


    /**
     * Compares two byte arrays in length-constant time. This comparison method
     * is used so that password hashes cannot be extracted from an on-line 
     * system using a timing attack and then attacked off-line.
     * 
     * @param   a       the first byte array
     * @param   b       the second byte array 
     * @return          true if both byte arrays are the same, false if not
     */
    private static boolean slowEquals(byte[] a, byte[] b)
    {
        int diff = a.length ^ b.length;
        for(int i = 0; i < a.length && i < b.length; i++)
            diff |= a[i] ^ b[i];
        return diff == 0;
    }

    /**
     *  Computes the PBKDF2 hash of a password.
     *
     * @param   password    the password to hash.
     * @param   salt        the salt
     * @param   iterations  the iteration count (slowness factor)
     * @param   bytes       the length of the hash to compute in bytes
     * @return              the PBDKF2 hash of the password
     */
    private static byte[] pbkdf2(char[] password, byte[] salt, int iterations, int bytes)
        throws NoSuchAlgorithmException, InvalidKeySpecException
    {
        PBEKeySpec spec = new PBEKeySpec(password, salt, iterations, bytes * 8);
        SecretKeyFactory skf = SecretKeyFactory.getInstance(PBKDF2_ALGORITHM);
        return skf.generateSecret(spec).getEncoded();
    }

    /**
     * Converts a string of hexadecimal characters into a byte array.
     *
     * @param   hex         the hex string
     * @return              the hex string decoded into a byte array
     */
    private static byte[] fromHex(String hex)
    {
        byte[] binary = new byte[hex.length() / 2];
        for(int i = 0; i < binary.length; i++)
        {
            binary[i] = (byte)Integer.parseInt(hex.substring(2*i, 2*i+2), 16);
        }
        return binary;
    }

    /**
     * Converts a byte array into a hexadecimal string.
     *
     * @param   array       the byte array to convert
     * @return              a length*2 character string encoding the byte array
     */
    public static String toHex(byte[] array)
    {
        BigInteger bi = new BigInteger(1, array);
        String hex = bi.toString(16);
        int paddingLength = (array.length * 2) - hex.length();
        if(paddingLength > 0) 
            return String.format("%0" + paddingLength + "d", 0) + hex;
        else
            return hex;
    }

    /**
     * Tests the basic functionality of the PasswordHash class
     *
     * @param   args        ignored
     */
    public static void main(String[] args)
    {
    	System.out.println(checkPasswordStrength("12121112"));
    	System.out.println(checkPasswordStrength("(*23;df+"));
    	System.out.println(checkPasswordStrength("(*23;+"));
    	System.out.println(checkPasswordStrength("(3;+"));
    	System.out.println(checkPasswordStrength("汉子"));
//    	System.out.println(System.currentTimeMillis());
//        try
//        {
//            // Print out 10 hashes
//            for(int i = 0; i < 10; i++){
//            	String salt = getSecureRandom();
//                System.out.println(PasswordUtil.createHash("p\r\nassw0Rd!", salt));
//            }
//
//            // Test password validation
//            boolean failure = false;
//            System.out.println("Running tests...");
//            for(int i = 0; i < 100; i++)
//            {
//            	String oldSalt = getSecureRandom();
//                String password = ""+i;
//                String hash = createHash(password, oldSalt);
//                String salt = getSecureRandom();
//                String secondHash = createHash(password, salt);
//                if(hash.equals(secondHash)) {
//                    System.out.println("FAILURE: TWO HASHES ARE EQUAL!");
//                    failure = true;
//                }
//                String wrongPassword = "1"+(i);
//                if(validatePassword(wrongPassword, oldSalt, hash)) {
//                    System.out.println("FAILURE: WRONG PASSWORD ACCEPTED!");
//                    failure = true;
//                }
//                if(validatePassword(password, oldSalt, hash)) {
//                    System.out.println("OK: GOOD PASSWORD ACCEPTED!");
//                    failure = false;
//                }
//            }
//            if(failure)
//                System.out.println("TESTS FAILED!");
//            else
//                System.out.println("TESTS PASSED!");
//        }
//        catch(Exception ex)
//        {
//            System.out.println("ERROR: " + ex);
//        }
//        
//        System.out.println(System.currentTimeMillis());
    }

}
